Power management for subscriber identity module

Abstract

A power management technique for a Subscriber Identity Module (SIM), makes use of a voting process to determine when to power-up and power-down the SIM. In particular, the voting process determines whether software modules running on a wireless communication device (WCD) require current or imminent access to the SIM. The voting process is designed to make more efficient use of the SIM without sacrificing performance. A modified security authorization process can be added, in which the WCD caches a user access code in memory for authenticating the user to the SIM to gain access to the secure features of the SIM. The security verification process avoids the need for the user to enter the access code each time the SIM is powered up in the course of the power management routine, reducing user inconvenience and maintaining performance.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application Ser. No. 60 / 271,789, filed Feb. 27, 2001, the content of which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The invention relates generally to wireless communication devices and, more particularly, to wireless communication devices that include a Subscriber Identity Module (SIM).BACKGROUND OF THE INVENTION[0003]A Subscriber Identity Module (SIM), such as a Removable User Identity Module (R-UIM), Universal Subscriber Identity Module (USIM), or GSM SIM, contains information relating to a user of a wireless communication device (WCD). A typical WCD may take the form of a cellular radiotelephone, satellite radiotelephone, a PCMCIA card incorporated within a computer, a PDA equipped with wireless communication capabilities, and the like.[0004]A SIM typically includes a controller and memory housed in a card-like structure. The memory may cont...

AI Technical Summary

Benefits of technology

[0009]The invention makes use of a voting process to determine when to power-up and power-down the SIM to support activities that require continuity of power. In particular, the voting process determines whether software modules running on the WCD require current or imminent access to the SIM before powering down the SIM. The voting process is designed to make more efficient use of the SIM with minimal or no impact on performance. In this manner, the invention is capable of reducing power consumption by a SIM, and thereby increasing battery duration and standby time for a WCD in which the SIM is installed.

[0010]The invention may also involve caching, in memory associated with the WCD, an access code for uniquely identifying a SIM user. With an R-UIM, for example, the access code may be a card holder verification (CHV) code. For a USIM, the access code may be a personal identification number (PIN). Unlike conventional systems in which a user keys the access code into the WCD each time the WCD, and hence the SIM, is powered-up, the WCD retrieves the cached access code from memory when the SIM is powered-up following a power-down initiated by a power management process. In this manner, the SIM can be powered up and down according to the voting process without requiring the user to repeatedly enter the access code, thereby reducing user inconvenience and maintaining WCD performance.

[0015]The invention is capable of providing a number of advantages. For example, the use of a voting process to determine when to power-up and power-down the SIM permits conservation of power without undermining SIM performance. In particular, before powering down the SIM, the voting process verifies that there are no pending requests and that no WCD software modules anticipate imminent generation of a request to be served by the SIM. In addition, caching the access code in the WCD relieves the user from the need to enter the information each time the SIM is powered-up for use in the course of power management. Thus, when the user powers the WCD up and down in normal operation, the user enters the access code. When power management results in powering down of the SIM, however, the WCD attends to retrieval of the access code from memory and sends it to the SIM for use by the SIM processor in authentication of the user.

Problems solved by technology

Power consumption by the SIM can be a significant factor in overall WCD power consumption.

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